The present invention relates to apparatus for forming a continuous tobacco stream, particularly for forming a stream which can be converted into a filler that is ready for draping into a web of cigarette paper or the like so as to constitute with the web a continuous rod which is thereupon subdivided into rod-shaped smokers' articles of unit length or multiple unit length. More particularly, the invention relates to improvements in distributors which can be used in cigarette rod making and analogous machines to convert a mass of tobacco shreds and/or otherwise configurated tobacco particles into a continuous stream which is ready for draping or is ready to be advanced into the range of one or more trimming or equalizing devices.
It is known to form a continuous tobacco stream in an elongated tobacco channel which is defined by two spaced-apart sidewalls and an endless air-permeable tobacco transporting conveyor. One side of the conveyor faces the channel and its other side is adjacent to a suction generating device serving to attract tobacco particles to the one side. The channel receives particles of tobacco in one or more streams of compressed air which are directed toward the one side of the conveyor and serve as carriers of the particles across the channel and into actual contact with the conveyor whereon the particles are retained by suction.
The forming of a tobacco stream in an apparatus of the above outlined character normally takes place by utilizing substantial quantities of compressed air some of which is used to transport tobacco particles and the remainder of which is used to classify the tobacco, i.e., to segregate satisfactory particles from unacceptable particles before the satisfactory particles are permitted to enter the channel at the one side of the tobacco transporting conveyor. In many instances, the quantity of air which is admitted into the channel exceeds the quantity which can be withdrawn through the air-permeable conveyor. Commonly owned U.S. Pat. No. 4,175,570, granted Nov. 27, 1979 to Uwe Heitmann, discloses the provision of suction ports in one sidewall of the distributor in a cigarette rod making machine and the placing of a suction chamber at the outer side of the one sidewall so that the surplus of air can be evacuated from the channel and the remainder of air can be withdrawn through the pores, interstices or otherwise configurated openings of the tobacco transporting conveyor. A drawback of the patented apparatus is that the rate of air flow through the ports of the one sidewall is limited and also that the pores are likely to be clogged with tobacco particles because they are immediately adjacent to the trajectories of such particles on their way toward the tobacco transporting conveyor. This can create serious problems and long-lasting interruptions in the operation of a rod making machine. Since a cigarette rod making machine can turn out in excess of 8000 plain cigarettes per minute, even short-lasting interruptions in the operation of such machines entail tremendous losses in output. The situation is aggravated whenever the channel is partially or completely clogged with tobacco particles because this almost invariably entails at least some clogging of suction ports in the patented apparatus.